SAT Subject Test Chemistry,10 edition

(A) 316.3   kcal

(B) 12.5    kcal

(C) –291.3  kcal

(D) –316.3  kcal

(E) 57.8    kcal

40 . Which of the following molecules is polar?

(A) BH 3

(B) NF 3

(C) C 2 H 6

(D) SF 6

(E) CCl 4

41 . Consider the following gas phase reaction:

H 2  (g)    +   Br 2    (g)     2HBr    (g)

The concentrations  of  H 2 ,   Br 2 ,  and HBr are 0.05    M,  0.03    M,  and 500.0   M,  respectively.   The

concentration   equilibrium constant    for this    reaction    at  400°C   is  2.5 ×    103 .  Is  this    system  at

equilibrium?

(A) Yes,    the system  is  at  equilibrium.

(B) No, the reaction    must    shift   to  the right   in  order   to  reach   equilibrium.

(C) No, the reaction    must    shift   to  the left    in  order   to  reach   equilibrium.

(D) It  cannot  be  determined.

(E) This    system  will    never   be  at  equilibrium.

42 . The Ka of acetic acid is 2 × 10 –5. What is the pH of a 0.5 M solution of acetic acid?